JP2752012B2 - Shift control method for continuously variable transmission for vehicle - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of calculating a target engine speed and an actual engine speed which are set in accordance with an index indicating a driver's intention to accelerate or decelerate, such as an accelerator pedal depression amount and an engine throttle opening. The present invention relates to a shift control method for a continuously variable transmission for a vehicle in which a speed ratio is controlled based on a difference.

[0002]

2. Description of the Related Art When performing such speed ratio control, the speed ratio is controlled so that the actual engine speed approaches the target engine speed.
It is necessary to appropriately set the magnitude of the change ratio of the gear ratio, that is, the gear speed so that desired characteristics can be obtained. For this reason, for example, Japanese Patent Publication No. 59-44537
The gear speed is changed according to the gear ratio, and the larger the gear ratio (= input speed / output speed),
A shift control method for increasing the shift speed is known. The purpose of this is to change the gear ratio at the time of starting quickly so that sufficient starting acceleration capability can be exhibited.

Japanese Patent Application Laid-Open No. 63-22737 discloses a shift control method in which the shift speed is changed according to the engine speed, and the shift speed is reduced as the engine speed increases. ing. The purpose of this is to secure shift responsiveness to an accelerator operation at low engine speed and to achieve shift stability at high engine speed.

[0004] In the above control device,
When the accelerator pedal is depressed during traveling and the target engine speed set in response to the depression is increased, a shift control for increasing the gear ratio (shifting to the LOW side);
A so-called kick down shift control is performed. Changes in engine speed, vehicle speed, and the like associated with this control will be described based on the model in FIG.

FIG. 11 shows a modeled vehicle in which the output of the engine E is transmitted to the wheels 120 via the power transmission mechanism 100. The continuously variable transmission is included in the power transmission mechanism. . The equivalent inertial mass of a rotating body directly connected to the output shaft of the engine E, that is, the rotating body of the engine system, is Ie, the output torque of the engine E is Te, and the output rotation of the engine is N
Then, the output torque Teo of the engine E when the accelerator pedal is depressed and the engine rotation increases.
(This is referred to as an engine transient torque) is expressed as: Teo = Te−Ie × dN / dt (1) That is, when the engine speed increases / decreases, the torque (Ie × dN / dt) is required for the acceleration / deceleration, so that the actually obtained output torque is Teo.

The output of the engine E is transmitted to the output shaft (axle) via the power transmission mechanism 100. Assuming that the reduction ratio of the power transmission mechanism 100 is i, the torque TDI transmitted to the output shaft is TDI = i × Teo = i × Te−i × Ie × dN / dt (2) in consideration of the equation (1). On the other hand, assuming that the rotation speed of the output shaft is ND, N = i
Since there is a relationship of × ND, this can be differentiated with respect to time and expressed as dN / dt = ND × di / dt + i × dND / dt (3)

Here, the equivalent inertial mass of the vehicle body system (not only the equivalent inertial mass of the vehicle body, but also the equivalent inertial mass of the wheels and their rotating bodies (tires, brake drums, axle shafts, etc.), the same as the final reduction gear input shaft) Assuming that a rotating body (including an equivalent inertial mass of a transmission counter shaft, an output gear, a propeller shaft, etc.) is ID, of the torque TDI transmitted to the output shaft as described above, the torque TDI is actually transmitted to the tire 120. The torque TD is: TD = TDI−ID × dND / dt (4)

Since the tire 120 is driven by this torque TD and the vehicle is accelerated, the acceleration α of the vehicle is expressed as Wα = Wα, where W is the mass of the vehicle, fRL is the running resistance of the vehicle, and r is the radius of rotation of the tire 120. TD / r-fRL (5) By substituting the above equation (4) into this equation (5), Wα = (TDI−ID × dND / dt) / r−fRL Further, by rearranging equations (2) and (3), Wα = i × Te / r − ｛(Ie × i ² / r + ID / r) × dN
D / dt + Ie × i × di / dt × ND｝ −fRL

Here, when r × ND = V (vehicle speed), r × dN /
Since dt = α (acceleration), ｛W + (Ie × i ² + ID) / r ² ｝ α = i × Te / r−
(Ie × i × ND / r) × di / dt-fRL (6) In this equation, when the constant term is replaced with A, B, C, or the like, A × α = B × Te−C × di / dt−D (7) As can be seen from the equation (7), when the accelerator pedal is depressed to perform the kick down shift, the engine torque Te increases in accordance with the depression of the accelerator pedal. Is increased, but the speed of change (di / dt) of the gear ratio due to kickdown acts to reduce the acceleration α.

For this reason, when the speed of the gear shift is too fast during the kick down shift, a state occurs in which the acceleration α becomes a negative value. In this case, the change in the acceleration (G) applied to the vehicle body and the change in the engine speed (Ne) are as shown in FIG. 9, for example. A situation occurs in which the rotation increases rapidly.

However, the kick down shift control is
In order to increase the driving force by increasing the gear ratio so as to reflect the driver's willingness to accelerate, the speed change control is performed. In this case, the above-described deceleration is a temporary operation. Even this is not desirable. Therefore, in general, the shift speed di / dt is set so that the acceleration α represented by the equation (7) does not become a negative value. With this setting, the change in acceleration (G) and the change in engine speed (Ne) applied to the vehicle body are as shown in FIG. 10, for example. Engine speed rises relatively smoothly.

[0012]

In the above-described shift control, in order to promptly reflect the driver's intention to accelerate, the shift speed di / dt is expressed by the following equation (7). It is preferable to set such that α is as large as possible within a range where α is a positive value. With this setting, the engine speed Ne can reach the target speed Neo in the shortest possible time during kick-down shifting without deceleration of the vehicle body. It becomes possible. However, when such a shift speed is set, in a situation where running conditions change little, such as constant speed running on a suburban road or the like, the engine rotation changes sensitively to a slight accelerator pedal operation or the like, There is a problem that driving feeling is impaired.

In order to avoid such a problem, the shift speed di
It is conceivable to set / dt lower than the maximum value in the range where the acceleration α represented by the equation (7) is a positive value. However, in this case, high mobility is required, such as when traveling on a mountain road or a road with many curves, and in a situation where there are many changes in running conditions, the change in the engine rotation becomes slow in response to an accelerator pedal operation or the like, There is a problem that it is not possible to perform a mobile run corresponding to such a change in the running conditions.

Further, when a kick down shift is performed while the engine is running at a high engine speed, the amount of increase in the engine speed is greater than a kick down at a low engine speed even at the same shift speed. For this reason, in the kick down shift at the high engine speed, there is a problem that the increase in the vehicle speed is felt more gently than the increase in the engine speed, which may give the driver a sense of idling of the engine.

Further, in such a kick down shift control, the shift control is performed at the shift speed set as described above until the actual engine speed matches the target engine speed. The engine speed rapidly increases until the engine speed approaches, and when the actual engine speed approaches the target engine speed, the rate of increase of the engine speed rapidly decreases. As a result, the kinetic energy that was continuously being added to the inertial mass of the engine during the rapid increase in the engine speed is added to the inertial mass of the vehicle body when the vehicle reaches the vicinity of the target engine speed, and the acceleration of the vehicle suddenly increases. I do. At this time, there is a problem that the driver may feel the acceleration as an impact. In particular, in a situation in which running conditions change little, such as running at a constant speed on a suburban road, the acceleration is higher than in a situation in which high mobility is required, such as running on a mountain road, a curved road, or the like. It can be said that the degree of feeling as a shock is high.

In the case where control is performed such that when the actual engine speed approaches the target engine speed, the rate of increase of the engine speed is rapidly decreased to make the actual engine speed coincide with the target engine speed, the actual engine speed is reduced. It often exceeds the target engine speed and overshoots. When an overshoot occurs, it is necessary to make a correction to restore the overshoot, but this correction may cause an undershoot. Then, the overshoot and the undershoot may alternately occur to cause hunting of the engine rotation.

The present invention has been made in view of the various problems that may occur during the kick down shift control described above, and provides a shift control method capable of performing a kick down shift control that meets a driver's requirement for traveling. With the goal.

[0018]

According to the present invention, in order to achieve such an object, an index (for example, engine throttle opening, accelerator operation amount, etc.) indicating a driver's intention to accelerate or decelerate is basically used in the present invention. The gear ratio is controlled so that the actual engine speed approaches the target engine speed set in accordance with the kick-down gear ratio change characteristic (the gear ratio change rate, that is, the gear ratio change ratio) in this gear ratio control. (A gain characteristic of the time change) is set in advance into a high-speed rotation region in which the engine rotation exceeds a predetermined rotation and a low-speed rotation region in which the engine rotation is equal to or lower than the predetermined rotation. Specifically, in the high-speed rotation region, a plurality of high-speed gear ratio change characteristics for kick-down speed change are set, and in the low-speed rotation region, the change characteristics are larger than any of these plurality of high-speed gear ratio change characteristics. A low speed gear ratio change characteristic having a gear ratio change rate is set.

When the actual engine speed is in the high-speed side rotation range, a plurality of types of high-speed side rotation are set according to the shift range set by operating the manual shift lever or the traveling mode set by operating the manual changeover switch. One of the speed ratio change characteristics is selected from among the speed ratio change characteristics, and when the actual engine speed is in the low speed rotation region, the low speed speed ratio change characteristic is selected. The shift control of the vehicle continuously variable transmission during the kick down shift is performed based on the characteristic. By performing such a kick-down shift control, not only can the shift range or the driving mode set by the driver's operation, that is, the kick-down shift control that matches the driving request based on the driver's operation be performed, It is possible to suppress the feeling of idling of the engine during kickdown at a high engine speed, and also to prevent overshoot of the actual engine speed.

In response to switching of the shift range or the driving mode, if it is possible to switch between a general driving characteristic and a high mobility driving characteristic in which mobility is better than the general driving characteristic, a high mobility is selected. The kick-down high-speed gear ratio change characteristic set when the driving characteristic is selected is the same as the kick-down high-speed gear ratio change characteristic set when the general driving characteristic is selected. It is desirable to have a characteristic that the rate of change of the speed ratio with respect to In this case, when the kick down speed ratio change characteristic in which the speed ratio change rate is substantially zero is set in a region where the engine speed is high, at least the speed ratio is in the region where the speed ratio change rate is substantially zero. In a region where the speed ratio is larger than the predetermined speed ratio, the engine speed is set to an engine rotation region where the engine speed is equal to or higher than a first predetermined high engine speed when the high mobility traveling characteristic is selected, and the first predetermined speed is selected when the general traveling characteristic is selected. It is desirable that the engine speed is set in an engine rotation region where the engine rotation speed is equal to or higher than a second predetermined high engine rotation speed lower than the high engine rotation speed.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings. First, FIG. 1 shows a hydraulic continuously variable transmission whose speed is controlled by the method according to the present invention.
The hydraulic continuously variable transmission TM includes a variable displacement hydraulic motor M having a constant discharge hydraulic pump P driven by an engine E via an input shaft 1 and an output shaft 2 driving wheels W.
And The pump P and the motor M are connected to a first oil passage La communicating the discharge port of the pump P and the suction port of the motor M, and a second oil passage Lb communicating the discharge port of the motor M and the suction port of the pump P. The two oil passages are connected to form a closed hydraulic circuit.

For this reason, when the pump P is driven by the engine E, the discharge oil from the pump P is sent to the motor M through the first oil passage La, and after the motor M is driven to rotate,
The oil is returned to the pump P through the second oil passage Lb. In this case, the oil pressure in the first oil passage La becomes high and the oil pressure in the second oil passage Lb becomes low. Also, when the engine brake is applied by receiving the driving force from the wheel W, such as when the vehicle is decelerating, the oil flow is the same, but the first oil passage La is at a low pressure and the second oil passage Lb is not. High pressure. On the other hand, the discharge port of the charge pump 10 driven by the engine E is connected to a hydraulic closed circuit via a charge oil passage Lg having a check valve 11 and a third oil passage Lc having a pair of check valves 3,3. . The hydraulic oil pumped up from the tank 15 by the charge pump 10 and adjusted in pressure by the charge pressure release valve 12 is supplied to the lower pressure side oil passage of the two oil passages by the action of the check valve 3.

Further, an oil passage L having a shuttle valve 4
d and the oil passage Lf having the clutch 5 are the first and second oil passages Lf.
It is arranged between the oil passages La and Lb. Shuttle valve 4
Is the oil passage Le of the oil passage La, Lb which has a low pressure.
The hydraulic oil in the closed circuit is returned to the tank 15 via the relief valve 6 via the relief valve 6. On the other hand, the clutch 5 is a valve that controls the degree of opening of the oil passage Lf. When the oil passage Lf is opened by this valve, the first
And the second oil passages La and Lb are short-circuited, and the discharge oil of the pump P flows through the short-circuit oil passage Lf and is not sent to the motor M. Therefore, if the opening degree control of the clutch 5 is performed, the clutch control of the transmission TM is performed.

The hydraulic motor M is, for example, a swash plate axial plunger motor, and its capacity can be controlled by controlling the swash plate inclination angle of the motor M. Here, the swash plate of the motor M is connected to the transmission servo unit 30 shown in FIG. Therefore, if the capacity of the variable displacement motor M is variably controlled by the shift servo unit 30, the speed ratio of the transmission TM (= the number of rotations of the input shaft 1 / the number of rotations of the output shaft 2) can be variably controlled. .

The transmission servo unit 30 will be described. The unit 30 includes a cylinder 31 and a piston rod 32 that is movably inserted left and right in the drawing into a cylinder hole 31a formed in the cylinder 31.
The opening end of the cylinder hole 31a is covered with the plug 33 with the piston rod 32 inserted, and the cylinder hole 31a
In this state, the inner space a is divided into two by the piston portion 32a of the piston rod 32, and left and right oil chambers 34 and 35 are formed. The cylinder 31 is formed with ports 31c and 31d communicating with the left and right oil chambers 34 and 35, respectively, and supplies and discharges hydraulic oil of a predetermined hydraulic pressure from the ports 31c and 31d to the left and right oil chambers 34 and 35, thereby forming a piston rod. 32 is moved left and right.

The piston rod 32 is connected to a variable displacement member (for example, a swash plate) of the motor M via a link mechanism 38, and variably controls the displacement of the motor M by moving the piston rod 32 left and right. You can do it. In this example, when the piston rod 32 is moved rightward, the gear ratio increases, that is, L
When the gear ratio changes to the OW side and moves to the left, the gear ratio decreases, that is, the gear ratio changes to the TOP side. Although not shown in this example, a servo mechanism that amplifies and transmits the moving force of the piston rod 32 may be provided in the link mechanism 38.

The ports 31c and 31d are connected to hydraulic lines 73 and 74, respectively.
4 is connected to the shift control valve 50. The shift control valve 50 includes a housing 51 and a first spring 54.
And first and second spools 52 and 53 which are slidably inserted in the housing 51 from side to side while being opposed to each other.
And a second spring 55 for urging the second spool 53 leftward.

A throttle cam 65 is in contact with the left end of the first spool 52, and the throttle cam 65 applies a rightward urging force corresponding to the throttle opening to the first spool 52. Therefore, the second spool 53 receives a rightward pressing force (hereinafter referred to as a first pressing force) corresponding to the throttle opening (that is, the amount of depression of the accelerator pedal) via the first spring 54. A governor pressure PG corresponding to the engine speed sent through the oil passage 71b acts on the right end of the second spool 53, and the second spool 53 applies a biasing force of the second spring 55 and the governor pressure PG. It also receives a leftward pressing force (this is referred to as a second pressing force) in combination with the corresponding hydraulic pressure. For this reason, the second pressing force is determined according to the difference between the first pressing force and the second pressing force.
The horizontal movement position of the spool 53 is determined.

The second spool 53 is provided with an oil passage 72 to which a control oil pressure Pc is supplied in accordance with the left-right movement.
And grooves 53a and 53b for communicating with the oil passage 73 or 74 connected to the ports 31c and 31d.
When the first and second pressing forces are balanced and the second spool 53 is located at the illustrated position, the oil passages 72, 7
3, 74 are all closed by the shift control valve 50, the piston rod 32 is held stationary at that position, and the gear ratio is maintained.

On the other hand, when the first pressing force becomes larger, for example, when the accelerator pedal is depressed, the second spool 53 is moved rightward, and the oil passages 72 and 73 are communicated via the groove 53a and the groove 53b is formed. The oil passages 74 and 75 communicate with each other via the. Therefore, the control oil pressure Pc is set in the left oil chamber 34.
Is supplied, the hydraulic oil in the right oil chamber 35 is discharged, the piston rod 32 is moved rightward, and the speed ratio is increased (shifted to the LOW side). Conversely, when the second pressing force is larger, the second spool 53 is moved leftward and the groove 5
The oil passages 72 and 74 communicate with each other via 3b, and the oil passage 73 communicates with the drain via the groove 53a. For this reason, the control oil pressure Pc is supplied into the right oil chamber 35, and the oil in the left oil chamber 34 is discharged, the piston rod 32 is moved to the left, and the gear ratio is reduced (the gear is shifted to the TOP side). .

In the above operation, the first pressing force is considered to be a force corresponding to the target engine speed as a first index indicating the acceleration / deceleration intention of the driver, and the second pressing force corresponds to the actual engine speed. Therefore, the speed ratio is controlled in accordance with the difference between the two pressing forces, that is, the difference between the target engine speed and the actual engine speed, and the speed ratio is controlled so as to reduce the difference. It can be said that it is done.

In such a speed change control, if the control is performed such that the second pressing force is larger and the speed ratio becomes smaller (changes to the TOP side), the gain of the change ratio of the speed ratio becomes If the first pressing force is larger but the gear ratio is controlled so as to be larger (change to the LOW side), the amount of discharged (drain) oil through the oil passage 75 Is controlled, and the gain of the change ratio of the gear ratio, that is, the gear speed is adjusted according to the engine speed and the like.

The discharge oil passage 75 is connected to the drain control valve 40 and has a solenoid valve 77 at the end.
To the oil passage 76 having The drain control valve 40 has a spool 42 movably inserted left and right into a housing 41 and a spring 43 for urging the spool 42 rightward. A governor pressure PG corresponding to the engine speed acts on the right end of the spool 42 via oil passages 71 and 71a. For this reason, when the governor pressure PG is low when the engine speed is equal to or lower than the predetermined speed, the spool 41 is moving rightward by the urging force of the spring 43, and the oil passage 75 is largely opened to the drain oil passage 77 via the groove 42a. .
However, when the engine rotation exceeds a predetermined rotation, the governor pressure PG exceeds the force of the spring 43, and the spool 41 is moved to the left.
Therefore, the communication opening between the oil passage 75 and the drain oil passage 77 is
As shown in FIGS. 3A and 3B, only the tapered notch 42b formed on the shoulder of the spool 41 is extremely small (substantially zero).

For this reason, (L
Oil path 7 when controlled to change to the OW side)
The amount of drain (drain) oil through 5 is large when the engine speed is equal to or lower than a predetermined speed, and becomes almost zero when the engine speed exceeds the predetermined speed. The amount of discharged oil is proportional to the moving speed of the piston rod 32, that is, the gain of the speed ratio change rate. The gain of the speed ratio change rate is large when the engine rotation is equal to or less than a predetermined rotation, and becomes substantially zero when the engine rotation exceeds the predetermined rotation. FIG. 4 shows the relationship between the gain and the engine speed. As shown by the solid line G1, when the engine speed is equal to or lower than the predetermined engine speed N1, the gain is a large value (K1) and rapidly increases near N1. The value decreases and becomes a very small value (K3 ≒ 0) in the higher engine rotation region.

However, the change in the gain is a change when the oil passage 76 is ignored.
Also affected by oil discharge through A solenoid valve 77 is connected to the end of the oil passage 76, and the oil passage 76
Of the solenoid valve 77 can be opened and closed by the valve body 77a of the solenoid valve 77. If the energization control of the solenoid valve 77 is performed and the valve body 77a is moved rightward, the tip end opening of the oil passage 76 is opened, and the drain oil passage 78
The oil is discharged via. Conversely, when the valve body 77a is moved to the left, the opening at the tip of the oil passage 76 is gradually closed, and the discharge of oil from the oil passage 76 is gradually reduced. The energization control of the solenoid valve 77 is performed by the control unit 80.
It is to be performed based on the control signal from
As can be seen from this, the control unit 80
Thus, the amount of oil discharged from the oil passage 76 can be controlled.

The maximum value of the amount of oil discharged through the oil passage 76, that is, the amount of oil when the front end opening of the oil passage 76 is fully opened, is determined when the spool 41 of the drain control valve 40 is moved to the right. It is set to be considerably smaller than the amount of oil discharged from the oil passage 77. Therefore, when the engine rotation is equal to or lower than the predetermined rotation N1 and the spool 41 of the drain control valve 40 is moved to the right to discharge the oil to the drain oil passage 77, most of the oil discharged from the oil passage 75 Flows into the drain oil passage 77. At this time, even if the amount of oil discharged from the oil passage 76 is controlled by controlling the operation of the solenoid valve 77, the total amount of oil discharged from the oil passage 75 is hardly affected.
Almost unchanged at 1.

However, when the engine rotation becomes equal to or higher than the predetermined rotation N1, the spool 4 of the drain control valve 40
When 1 is moved to the left and the oil discharge to the drain oil passage 77 becomes almost zero, the amount of oil discharged from the oil passage 76 determined by the operation control of the solenoid valve 77 becomes the total discharge from the oil passage 75. It greatly affects the quantity. Therefore, in this case, by controlling the operation of the solenoid valve 77, the gain of the speed ratio change rate can be controlled. By such control, for example, in FIG.
When the engine speed becomes equal to or higher than the predetermined speed N1, the oil discharge amount from the oil passage 76 is controlled so as to have a constant value, and a setting is made so as to have a constant gain K2. it can. Further, in FIG.
As shown by, it is also possible to set such that the discharge of oil from the oil passage 76 is gradually reduced in accordance with the increase in the engine speed, and the gain K is gradually reduced.

As shown in FIG. 2, the control unit 80 for outputting a control signal for setting the gain includes a vehicle speed signal V detected by a vehicle speed sensor 81,
The gear ratio signal i detected by the gear ratio detection sensor 82,
The throttle opening signal θth detected by the engine throttle sensor 83, the engine intake pressure signal Pb detected by the negative pressure sensor 84, the engine rotation signal Ne detected by the rotation sensor 85, the accelerator opening sensor 86
, The shift angle signal RP detected by the shift lever position sensor 87.
Running mode signal M from mode changeover switch 88
D is inputted, and based on these signals, the solenoid valve 7 is
7 is output.

In this embodiment, a plurality of gain characteristics (speed ratio change characteristics) of the speed ratio change rate in the kick down shift are set in advance, and the plurality of gain characteristics are set in accordance with a second index indicating a driver's request for traveling. A predetermined characteristic is selected from various types of gain characteristics, and kickdown shift control is performed based on the selected characteristic.

Specifically, for example, in FIG. 5, a gain characteristic G4 in which the gain is K4 in a region above the predetermined engine speed N1 as shown by a broken line, and a predetermined engine speed N1 as shown by a dashed line. The gain characteristic G5 in which the gain in the above-mentioned region is K5 is set, and this is appropriately selected according to the second index to perform kickdown shift control. As the second index, for example, a shift range can be used. When the shift range is in the D range (when the shift lever is in the D position), the driver requests relatively gentle driving, that is, general traveling characteristics, and when the shift range is in the L range (when the shift lever is in the L position). In this case, it is considered that the driver demands crisp driving with high mobility, that is, high mobility driving characteristics, and the shift characteristics are set so that the driving characteristics correspond to this requirement.

In this example, the gain characteristic G4 is selected in the case of the D range, and the gain characteristic G5 is selected in the case of the L range.
Is to be selected. Therefore, when the kick down shift is performed in the L range, the gain K is relatively large.
5 is set, and the engine speed at the time of gear shifting rapidly approaches the target engine speed Neo as shown by the solid line L in FIG. On the other hand, when the kick down shift is performed in the D range, a gain K4 smaller than the gain K5 in the L range is set, and the engine speed during the shift is gradually reduced to the target engine speed as shown by a broken line D in FIG. It approaches rotation Neo.

FIG. 7 shows actual speed ratios and changes in engine speed when such control is performed. In this figure, the vertical axis shows the engine speed, the horizontal axis shows the vehicle speed, the vertical axis corresponds to the transmission input rotation, and the horizontal axis corresponds to the transmission output rotation. For this reason, the inclination of the straight line extending from the origin represents the speed ratio i, and the speed ratio is controlled in the range from imax to imin. This figure shows a shift control result when the accelerator pedal is depressed until the throttle is fully opened while the vehicle is running with the engine throttle opening fully closed. As described above, since the gain characteristics selected between the D range and the L range are different, the shift control result also shows that the change in the D range (the change indicated by alternate long and short dash lines D1, D2, and D3) is as shown in FIG. The change is more gradual than the change in the L range (change indicated by solid lines L1, L2, L3).

By performing the above-described control, the shift response to the accelerator operation is improved in the L range where high mobility characteristics are required. For this reason, mountain roads,
When high mobility is required, such as when traveling on a road with a lot of curves, setting the L range provides a high shift response to accelerator operation during kick down, and a kick that matches the high mobility driving characteristics. Downshift control is performed. On the other hand, in the D range where general running characteristics are required, the shift responsiveness to the accelerator operation at the time of kick down becomes gentle. For this reason, in a driving situation in which running conditions change little, such as constant-speed running on a suburban road or the like, fluctuations in engine rotation that are too sensitive to a slight operation of the accelerator pedal can be suppressed. As a result, quiet and stable running that matches the general running characteristics can be realized.

In the above, the case where the shift range is used as the second index indicating the driver's request for traveling has been described. However, the present invention is not limited to this, and the following is used. be able to. For example,
There is a mode changeover switch that is switched by a driver's operation. For example, the mode changeover switch can select between an economy mode that requires general driving characteristics and a sports mode that requires high mobility driving characteristics. For this reason,
When the economy mode is set, the gain characteristic G4 in FIG. 5 is selected, and when the sport mode is set, the gain characteristic G5 is selected.

The accelerator opening θAP, the rate of change of the accelerator opening θAP, the throttle opening θth, the rate of change of the throttle opening θth, the engine intake pressure Pb, and the rate of change of the engine intake pressure Pb can also be used as the second index. it can. Specifically, for example, when the change rate of the accelerator opening θAP is small, it is considered that the general driving characteristic is required, and the gain characteristic G4 in FIG. 5 is selected, and the change rate of the accelerator opening θAP is large. , It is assumed that the high mobility performance is required, and the gain characteristic G5 in FIG. 5 is selected.

When setting the gain characteristic (gear ratio change characteristic) at the time of kick down as described above, in a region where the engine speed is high, the gain K is substantially zero, that is, the gear ratio is hardly changed. There are times when you do. This is because, in the high engine speed region, the change in the engine speed with respect to the change in the gear ratio becomes sharp, so if the kick down shift is performed while the engine is running at a high speed, the engine speed is prevented from rising excessively, Further, it is to prevent the increase in the vehicle speed from being felt more slowly than the increase in the engine rotation and giving the driver a sense of idling of the engine. In a region where the gain K is substantially zero, the engine speed only increases in response to the depression of the accelerator pedal while the speed ratio remains constant with respect to the depression of the accelerator pedal. For this reason, in this region, the shift responsiveness to the accelerator operation becomes low, so in the present invention, this region is also set in accordance with the second index indicating the driver's request for traveling.

Specifically, when a second index for general driving characteristics, for example, a D range is set, a gain characteristic such that the gain K becomes zero in regions B and C in FIG. 8 is selected. I do. As a result, the gain K becomes zero in a region B where the speed ratio is larger than the predetermined speed ratio i0 and the engine speed is larger than N3, and in a region C where the engine speed is larger than N2. On the other hand, when the second index for the purpose of high-mobility traveling characteristics, for example, the L range is set, a gain characteristic such that the gain K becomes zero only in the region C in FIG. 8 is selected. As a result, the gain K becomes zero only in the region C where the engine rotation is larger than N2.

That is, in this control, in the gain characteristic (speed ratio change characteristic) selected when the second index for the general traveling characteristic is set, the second index for the high mobility traveling characteristic is selected. The region where the gain is almost zero is set wider than in the gain characteristic selected when is set. By setting in this way, while maintaining quiet and stable running in general running characteristics,
It is also possible to secure high mobility traveling with high mobility traveling characteristics.

In the above, the case of a hydraulic continuously variable transmission has been described as an example. However, the present invention is not limited to this, and it is a matter of course that the present invention can be used for other types of continuously variable transmissions. That is. Although the solenoid valve 77 is used in this embodiment as a means for adjusting the gain of the speed ratio change rate, the present invention is not limited to such a configuration and controls the amount of oil flowing through the oil passage 76. The configuration does not matter as long as it is possible. Furthermore, instead of controlling the drain oil amount in this way, a means that directly controls the moving speed of the piston rod of the servo unit may be used.

[0050]

As described above, according to the present invention,
A plurality of high-speed gear ratio change characteristics for a kick-down shift are set in a high-speed rotation region in which the actual engine rotation speed exceeds a predetermined rotation speed, and the high-speed gear ratio change characteristics in the low-speed rotation region are larger than any of these high-speed gear ratio change characteristics. A low-speed side shift change characteristic having a speed ratio change rate is set. In a high-speed side rotation region, a plurality of types are set according to a shift range set by operating a manual shift lever or a traveling mode set by operating a manual changeover switch. Since any one of the gear ratio change characteristics is selected from among the gear ratio change characteristics, and the gear change control at the time of kick down is performed based on the selected gear ratio change characteristic, first, the driver's operation is performed. The kick down shift control that matches the shift range or the driving mode set by the above, that is, the driving request based on the driver's operation is performed. It is possible. Further, since the low-speed gear ratio change characteristic is set to have a larger gear ratio change rate than the high-speed gear ratio change characteristic, the feeling of idling of the engine during kickdown at a high engine speed is suppressed,
Overshoot of the actual engine rotation can be prevented, and the shift feeling during kick down can be improved.

In response to the switching of the shift range or the driving mode, if the general driving characteristic and the high driving characteristic which makes the driving better than the general driving characteristic can be selected, the high driving characteristic can be selected. The kick down gear ratio change characteristic set when the driving characteristic is selected is smaller than the kick down gear ratio change characteristic set when the general driving characteristic is selected. It is desirable to have the property of increasing the rate. In this case, when a kickdown speed ratio change characteristic in which the speed ratio change rate is substantially zero is set in an area where the engine speed is high, the area in which the speed ratio change rate is substantially zero is
At least in a region where the speed ratio is larger than the predetermined speed ratio, the engine speed is set to an engine speed region where the engine speed is equal to or higher than the first predetermined high engine speed when the high mobility driving characteristic is selected, and when the general driving characteristic is selected. Is desirably set to an engine rotation region that is equal to or higher than a second predetermined high engine speed lower than the first predetermined high engine speed. When such a speed ratio change characteristic is set, a quiet and stable kick down shift characteristic is ensured when the general driving characteristic is set, and when a high mobility driving characteristic is set,
It is possible to secure a quick kick down shift characteristic with high mobility.

[Brief description of the drawings]

FIG. 1 is a hydraulic circuit diagram showing a configuration of a hydraulic continuously variable transmission whose speed is controlled by a method according to the present invention.

FIG. 2 is a hydraulic circuit diagram showing a shift control device of a hydraulic continuously variable transmission whose shift is controlled by the method according to the present invention.

FIG. 3 is a cross-sectional view and a plan view showing a drain control valve spool constituting the control device.

FIG. 4 is a graph showing a relationship between a gain of a speed ratio change rate and an engine speed.

FIG. 5 is a graph showing a relationship between a gain of a speed ratio change rate and an engine speed.

FIG. 6 is a graph showing a change in engine speed during a kick down shift.

FIG. 7 is a graph showing changes in engine speed and gear ratio during a kick down shift.

FIG. 8 is a graph showing a region where the gain becomes substantially zero when setting the gain characteristic of the speed change ratio.

FIG. 9 is a graph showing a change in acceleration acting on the vehicle body and a change in engine speed during a kick down shift.

FIG. 10 is a graph showing a change in acceleration acting on a vehicle body and a change in engine speed during a kickdown shift.

FIG. 11 is a schematic diagram illustrating a power transmission system model of a vehicle.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Input shaft 2 Output shaft 4 Shuttle valve 5 Clutch 30 Transmission servo unit 40 Drain control valve 50 Transmission control valve 65 Throttle cam 77 Solenoid valve 80 Control unit

────────────────────────────────────────────────── (5) Continuation of the front page (51) Int.Cl. ⁶ Identification code FIF16H 59:24 59:42 59:70 (56) References JP-A-2-150562 (JP, A) JP-A-3-121349 (JP, A) JP-A-3-204457 (JP, A) JP-A-62-125923 (JP, A) JP-A-62-139731 (JP, A) JP-A-62-139732 (JP, A) ( 58) Field surveyed (Int.Cl. ⁶ , DB name) F16H 61/00-61/24 F16H 61/40-61/46

Claims (3)

(57) [Claims] A target engine speed is set in accordance with an index indicating a driver's intention to accelerate or decelerate, such as an engine throttle opening and an accelerator operation amount, so that an actual engine speed approaches the target engine speed. In the shift control method for a continuously variable transmission for a vehicle, the speed ratio of which is controlled in the high speed side rotation region where the actual engine rotation speed exceeds the predetermined rotation speed set in the practical rotation speed range, A plurality of types of high-speed gear ratio change characteristics for kickdown shifting are set, and a low-speed rotation region in which the actual engine speed is equal to or lower than the predetermined speed is lower than any of the plurality of high-speed gear ratio change characteristics. A low-speed gear ratio change characteristic having a large gear ratio change rate is set, and when the actual engine speed is in the high-speed rotation region, a gear set by operating a manual shift lever is set. One of the plurality of types of high-speed gear ratio change characteristics is selected according to the drive mode set by operating the shift range or the manual changeover switch, and the actual engine speed is reduced to the low-speed gear ratio. A speed change control for a continuously variable transmission for a vehicle, wherein the speed change control during the kick down shift is performed based on the selected speed ratio change characteristic when the vehicle is in the rotation range. Method. 2. In accordance with switching of the shift range or the traveling mode, switching between a general traveling characteristic and a high mobility traveling characteristic in which mobility is better than the general traveling characteristic can be selected. The high-speed side gear ratio change characteristic selected when the mobile driving characteristic is selected is compared with the high side gear ratio change characteristic set when the general driving characteristic is selected.
2. The speed change control method for a continuously variable transmission for a vehicle according to claim 1, wherein the speed change ratio for the same engine speed has a characteristic of increasing. 3. A speed change ratio characteristic for a kick-down shift in which a change ratio of a speed ratio is substantially zero is set in the high speed side rotation region, and a speed ratio change characteristic in which the change ratio of the speed ratio is substantially zero. Is set to an engine rotation region in which at least a first predetermined high engine rotation speed in the high speed rotation region when the high mobility traveling characteristic is selected, at least in a region where the speed ratio is larger than a predetermined intermediate speed ratio. When the general driving characteristic is selected, the engine speed is set to an engine rotation region within the high speed rotation region that is equal to or higher than a second predetermined high engine rotation speed lower than the first predetermined high engine rotation speed. The shift control method for a continuously variable transmission for a vehicle according to claim 2, wherein